Monument record MHG9614 - Promontory Fort, Dun Mhairtein

Dun Mhairtein (NR) OS 6"map, Sutherland, 2nd ed., (1964)

Dun Mhairtein is promontory fort with a 'blockhouse'- type forework, probably dating from 1st century BC or slightly earlier, whose surviving internal arrangement owes nothing to broch or post-broch occupation which occurs on most other forework-type forts on N mainland.
A precipitous cliff promontory about 27m high, curves parallel with mainland, from which it is separated by a geo. The fortification cuts off tail of promontory, enclosing area 22m by 24m which is over-looked by higher cliff on mainland side of geo.
The main feature is a stone-revetted rampart 4.2m thick at W end, 5m wide at E and 1.2m to 1.8m high, pierced slightly E of centre by an entrance passage 1.02m. wide at outer end and widening inwards. An upright slab, set at right angles two-thirds of way along passage, forms a doorcheck. The ends of the rampart fade away towards cliff-edge and in front of it the ground has been scooped back from either edge, leaving a causeway, 2.5m wide, in line with the entrance. On W side only, a bank, apparently of loose material and unrevetted, intervenes between rampart and ditch. It is about 3.6m thick and is separated from rampart by a gap of 3m. The ditch on this side descends to brink in 3 broad steps. It is possible interior of fort has been enclosed by a wall following cliff-edge, as traces can be seen running N from each end of rampart.
Within fort and about 8.3m back from rampart is a complex of structures forming a shapeless mound in which part of interior of a rectilinear hut has been exposed quite recently, the visible portions being SE wall, 2.74m long, and parts of SW and NE walls. The rest of interior is choked with debris. It is well-constructed of orthostats, 0.9m high, topped by fine dry-stone walling now preserved to a height of 0.3m at SW corner where topmost courses oversail slightly, although this may be due to bulging. In debris is a possible lintel 1.2m long and 0.25m square.
A deep depression 3m to NW gives access to, and possibly represents collapsed terminal chamber of a souterrain which runs NE and downwards, following ground slope for 10.7m, and emerging in cliff-face where there is a slight ledge 1.2m below the cliff-edge.
Here passage is 0.8m wide expanding to 1.1m in depression on SW. Although it is choked with debris to within 0.5m of roof it is possible to see along whole length of it. The roof is of heavy lintels on orthostats and dry-walling and is broken in 3m from entrance, at which point there are many earthfast slabs.
Resurveyed at 1:2500 in 1972 and revised in 1977.
RCAHMS 1911, visited 1909; R G Lamb 1980; R J Mercer 1981; Visited by OS (W D J) 3 May 1960, (A A) 8 November 1972 and (J B) 6 June 1977.